There exists in the prior art many aqueous cleaning solutions for industrial and commercial uses which contain a mixture of enzymes, as well as surfactants, detergents and other components. Enzymatic cleaning solutions have also been used in the past to clean various instruments, particularly medical instruments that have been soiled by exposure to materials and microorganisms present in the body cavities, tissues and blood of the surgical patient. Enzymes taught to be useful in such cleaning applications include one or more protease, amylase, lipase, cellulase and pectinase enzymes, which serve to attack or degrade organics, such as proteins, starches, fats, cellulose and pectins.
Medical and dental instruments are typically immersed in enzyme cleaners for the removal of gross soils prior to cleaning and disinfecting/sterilization. In order to effectively disinfect and/or sterilize these instruments, they must be scrupulously cleaned. The introduction of flexible glass fiber endoscopes and their growing use has created a challenge to effective cleaning. These instruments are complicated in design and contain a number of different materials. Typically the endoscopes utilize narrow lumens to transport air, liquids and surgical instruments to the interior of the human body, thereby making the instrument very difficult to clean.
Current methods of pre-cleaning medical instruments involve rinsing the instrument with water or cleaning solutions immediately after patient use. The instruments are then soaked in an enzyme solution until delivery to a central cleaning area where the instrument is disinfected and sterilized, usually by an autoclave. The enzyme soaking solution keeps the instrument moist in addition to digesting the proteinaceous, cellulosic, fat and other tissue adhering to the instrument surfaces. If the surfaces of the instrument become dry prior to cleaning, incomplete cleaning can result, which in turn may adversely impact subsequent disinfecting and/or sterilization.
There are several major drawbacks to using current immersion cleaning solutions to pre-clean complex modem medical instruments such as endoscopes. First of all, there is the tendency of the solution to splash during transport to the central cleaning area. Secondly, current enzymatic cleaning solutions typically lack antimicrobial agents to prevent growth of organisms introduced into the solution by the soiled instruments. In addition, continued use of a soaking solution tends to promote corrosion due to the variety of different materials utilized in the manufacture of the endoscopic instruments.
The present invention relates to a novel method and composition for pre-cleaning medical instruments and other devises that need to be kept moist to facilitate a final cleaning. In its preferred embodiments, a unique enzymatic cleaner is applied and maintained as a foam directly on the instrument surfaces without the need for immersion or heating.
The following are examples in the patent literature of several prior art cleaners and methods which utilize them:
Metesky et al, U.S. Pat. No. 5,462,607, Method of Cleaning Using A Foamed Liquid, teaches the use of an aqueous solution containing a surfactant and enzymes which is heated to create a foam via ebullition. This cleaner is useful for cleaning industrial equipment which has been soiled by lubricants.
Disch et al, U.S. Pat. No. 5,234,832, Process For Cleaning And Disinfecting Heat And Corrosion Sensitive Medical Instruments, teaches the use of a cleaning solution for endoscopes which contains a low-foaming nonionic surfactant, a proteolytic enzyme, a complexing agent and an aldehyde disinfectant in water having a specific hardness. The endoscope is immersed in the cleaning solution and heated to 550 C. to 650 C. for one to fifteen minutes, after which the instrument is rinsed and dried.
Disch et at, U.S. Pat. No. 5,233,166, Preparation And Processes For Cleaning And Disinfecting Endoscopes, is directed to a composition which is useful in the process described in U.S. Pat. No. 5,234,832.
Benson, U.S. Pat. No. 5,489,531, Combined Two Stage Method For Cleaning And Decontaminating Surgical Instruments, describes a method for cleaning and decontaminating soiled surgical instruments by immersing the instruments in an enzyme cleaning solution and then adding a germicidal detergent microbiological decontaminating solution.
Van Duzee et al. U.S. Pat. No. 5,576,278, Stable Liquid Enzyme Compositions And Methods of Use, teaches the cleaning of contact lenses by immersion in compositions containing opthalmically acceptable enzymes of high purity.
Smitkowski et al. U.S. Pat. No. 5,810,944 discloses a composition for cleaning surgical instruments comprising at least two C.sub.5 -C.sub.10 alkyl sulfate salts, at least one formulation aid such as polyethylene glycol, at least one alkanolamine and sodium sulfonate, and at least one proteolytic enzyme, along with optional conventional complexing agents and conventional preservatives.